Electroacoustic transducer

ABSTRACT

A small earphone or headphone which can produce a wide band acoustic output from a low-pitched tone to a high-pitched tone and can generate a body-sensitive vibration independent output or a body-sensitive vibration output synchronized with a music. The earphone or headphone is mounting a vibration actuator which is provided with a magnetic circuit including a permanent magnet, a yoke, and a plate for concentrating the flux of the permanent magnet, with a coil disposed in an air gap of the magnetic circuit, with a diaphragm fixed with the coil and being imparted with a driving force therefrom, and with a vibration transmitting section for supporting the magnetic circuit flexibly through a suspension comprising a flexible spring.

TECHNICAL FIELD

The present invention relates to an earphone or headphone that is smallin size and can produce a body sensible vibration such as a tactilesound, a vibration sound, or a conduction sound (hereinafter a bodysensible vibration) and a wideband sound.

BACKGROUND ART

FIGS. 4 and 5 are partly-broken side views of a conventional typicalearphone and a conventional typical headphone, respectively. As shown inFIG. 4 or 5, the conventional earphone or the conventional headphone ofthe type incorporates a small-sized speaker 21 with an outside dimensionof 13 mm or 30 mm and a height of 2 to 7 mm and thereby has a functionof producing a sound. There has also been such an earphone or headphonecommercially available that incorporates, separately from the speaker21, a vibrating member 4 serving as a vibration generation source asshown in FIG. 6 or 7 in order to further achieve a body sensiblevibration function. However, an outside dimension thereof is 25 mm ormore.

In order to generate a sound and a body sensible vibration, theconventional earphone or headphone of the type must be mounted with therespective individual components therefor. Consequently, there have beenproblems of an increase in cost of the components, an increase inmounting space, complexity of a control circuit, an increase inassembling cost, and so forth. Further, there has been a problem that,since the sound generating component such as the speaker is small insize and diameter, an output of low-pitched tone is small and thereforea wideband acoustic output cannot be produced.

It is therefore an object of the present invention to provide anearphone or headphone that is small in size and can produce an output ofbody sensible vibration and a wideband acoustic output from alow-pitched tone to a high-pitched tone, thereby solving theabove-mentioned problems.

DISCLOSURE OF THE INVENTION

According to the present invention, there is obtained an earphone orheadphone having a vibration actuator mounted as an electroacoustictransducer, the vibration actuator comprising a magnetic circuitcomposed of a permanent magnet, a yoke, and a plate used forconcentrating magnetic flux of the permanent magnet, a coil disposed inan air gap of the magnetic circuit, a vibrating plate attached with thecoil and imparted with a driving force by the coil, and a vibrationtransmitting portion flexibly supporting the magnetic circuit through asuspension formed by a flexible spring.

Further, according to the present invention, there is obtained theearphone or headphone, wherein, by simultaneously inputting a lowfrequency signal for generating a body sensible vibration and a signalfor generating a sound and having a frequency higher than that of thelow frequency signal, the vibration actuator simultaneously generatesthe body sensible vibration and the sound.

Further, according to the present invention, there is obtained theearphone or headphone, wherein, in the vibration actuator, the magneticcircuit vibrates in response to an input signal of a low-band frequencythat generates a body sensible vibration and a low-pitched tone, both ofthe vibrating plate and the magnetic circuit vibrate in response to aninput signal of an intermediate-band frequency, and the vibrating platevibrates in response to an input signal of a high-band frequency toproduce a high-pitched tone.

Thus, as a vibration actuator in which, by applying a wideband signal toa coil, the coil located in a magnetic circuit vibrates, or the magneticcircuit vibrates, or both the coil and the magnetic circuit vibrate, tothereby transmit the vibration to the exterior through a support, or thevibration of a vibrator is transmitted as an acoustic output produced byair vibration, the vibration actuator according to the present inventionis characterized in that the body sensible vibration and the sound cansimultaneously be produced. Accordingly, the present invention providesnew media enabling information transmission including representation ofemotions by the use of the sound and the body sensible vibration, thatis not achieved in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view, partly sectioned, showing anearphone according to an embodiment of the present invention.

FIG. 2 is an external perspective view, partly sectioned, showing aheadphone according to an embodiment of the present invention.

FIG. 3 is a sectional view of a vibration actuator mounted in each ofthe earphone and the headphone of FIGS. 1 and 2.

FIG. 4 is an external perspective view, partly sectioned, showing aconventional earphone.

FIG. 5 is an external perspective view, partly sectioned, showing aconventional headphone.

FIG. 6 is an external perspective view, partly sectioned, showing aconventional earphone having a vibration generating function.

FIG. 7 is an external perspective view, partly sectioned, showing aconventional headphone having a vibration generating function.

FIG. 8 is a sectional view showing another vibration actuator mounted inthe earphone or headphone according to the present invention.

FIG. 9 is a plan view showing a half of an inner surface of only a lowercover in FIG. 8.

FIG. 10 is a sectional view showing still another vibration actuatormounted in the earphone or headphone according to the present invention.

FIG. 11 is a bottom view of the vibration actuator of FIG. 10.

FIG. 12 is a graph showing vibration sound pressure characteristics of aprior art product and FIG. 3.

FIG. 13 is a graph showing conduction power characteristics of a priorart product and FIG. 3.

FIG. 14 is a graph showing sound pressure characteristics in case ofpresence of air holes in a vibrating transmitting portion having astepped structure in the present invention (FIG. 10) and in case ofabsence of air holes (prior art).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, an electroacoustic transducer according to embodiments ofthe present invention will be described with reference to the drawings.

Referring to FIGS. 1 and 2, outside diameters of vibration actuators 3mounted in an earphone and a headphone shown in these figures are 13 mmand 17 mm, respectively, and it is therefore possible to realizeelectroacoustic transducers each having an outside diameter not greaterthan 20 mm.

In the vibration actuator 3 used in FIG. 1 or 2, a magnetic circuit hasan internal magnet structure in which a disc-shaped permanent magnet 32is interposed between a yoke 31 and a plate 33, as shown in FIG. 3. Acircular magnetic gap G is formed at a portion thereof. A center shaft37 having a shape of a bolt, a pin, or the like is fitted into a centerhole of the magnetic circuit to thereby position the yoke 31, thepermanent magnet 32, and the plate 33 on the same axis. A suspension 34comprises a single piece of an arc-shaped helical leaf spring andflexibly supports the magnetic circuit. Specifically, an inner endportion of the helical leaf spring is fixed to an outer peripheralportion of the yoke 31 by bonding using an elastic material, such as apressure sensitive adhesive, an adhesive, or a resin, or by caulking orthe like, while an outer end portion thereof is fixed to a vibrationtransmitting portion 38.

On the other hand, a coil 36 is fixed to a diaphragm 35 provided with acoil fixing portion 39 having a recessed shape, and may be cemented withan adhesive or the like if necessary. The coil 36 is disposed in themagnetic gap G of the magnetic circuit.

The vibration transmitting portion 38 is provided with a stopper 40. Thestopper 40 serves to prevent a collision between the magnetic circuitand the diaphragm 35 when the excessive power is applied to thevibration actuator.

The magnetic circuit may have an external magnet structure or a radialstructure instead of the internal magnet structure of FIG. 3. Theorientation of magnetic poles of the permanent magnet 32 may be eitherdirection as long as it is an axial direction.

The suspension 34 is formed integral with the vibration transmittingportion 38 by insert molding, welding, bonding, or the like.

Normally, the diaphragm 35 is formed by a sheet-like film or cone paperand may have a planar shape, a dish-like shape, a curved surface shape,a corrugate shape, or a shape obtained by combining these shapes. Incase of the curved surface shape, a single curvature or a combination ofdifferent curvatures may be adopted. The diaphragm is designed so as toachieve a predetermined acoustic property by such a combination and athickness. In order to obtain a larger amplitude of the diaphragm 35, anouter peripheral portion of the diaphragm 35 may be fixed to thevibration transmitting portion 38 through an elastic material such as apressure sensitive adhesive, an adhesive, or a resin if necessary. Athrough hole for air bleeding may be provided at a center portion of thecenter shaft 37.

The vibration transmitting portion 38 is made of a resin or the likethat exhibits elastic action, and is formed into a case-like shapehaving a hollow portion for containing the magnetic circuit, thesuspension 34, the diaphragm 35, and the coil 36. An upper cover 41 anda lower cover 42 closing upper and lower openings of the hollow portionare provided. The vibration transmitting portion 38, the upper cover 41,and the lower cover 42 form a cavity. For example, sound release holes43 are optionally formed in the lower cover 42 so that the cavitysatisfies the principle of the Helmholtz resonator. Attention must bepaid so as not to allow the air to flow into or flow out from the cavityexcept through the sound release holes 43.

Note that the lower cover 42 also serves to prevent plastic deformationof the suspension 34 due to excessive vibration of the magnetic circuit.

The vibration transmitting portion 38 has a terminal table 44 integrallyformed at a portion of its outer side surface and projecting outward. Aterminal 45 is formed on the terminal table 44 and a lead wire 46 of thecoil 36 is connected to the terminal 45. A signal for driving is appliedto the coil 36 from this terminal 45.

In the vibration actuator of FIG. 3, let a signal of a single frequencyaround 100 Hz be input to the coil 36. In this event, since the coil 36is located in the magnetic gap G of the magnetic circuit, the coil 36and the magnetic circuit vibrate relative to each other insynchronization with the input frequency according to the Fleming's lefthand rule. This vibration is output to the exterior from the vibrationactuator through the vibration transmitting portion 38. This is a bodysensible vibration and is a low-pitched tone as a sound.

When a signal of a single frequency around 2 kHz is input to the coil36, the coil 36 and the magnetic circuit vibrate relative to each otherin synchronization with the input frequency and the vibration of thecoil 36 is transmitted to the diaphragm 35 to vibrate the diaphragm 35.This vibration falls within the human audible range because of its highfrequency and thus can be heard as a sound. In this event, the vibrationof the magnetic circuit is simultaneously transmitted through thevibration transmitting portion.

On the other hand, when a voice or music signal of several hundred toseveral thousand Hz is input into the coil 36, the diaphragm 35vibrates. Since the diaphragm 35 is normally formed by a sheet-like filmor cone paper, this vibration actuator can output a voice or music likean ordinary speaker.

As described above, the vibration of the vibration actuator of theearphone or headphone of the present invention has a wideband frequencyspectrum characteristic. For example, as shown in characteristic graphsof FIGS. 12 and 13, a vibration sound is about 55 dBSPL at 100 Hz, whilea conduction power is about 0.55 G at 400 Hz. From this, the sound andthe body sensible vibration can be output individually or simultaneouslyso that highly diversified expressions are made possible as comparedwith a simple motor sound of a conventional vibration motor.

In the above-mentioned vibration actuator, a resonance frequency of themagnetic circuit is determined from a weight of the magnetic circuit anda spring constant of the suspension 34. Therefore, the resonancefrequency of the magnetic circuit can be synchronized with a bass soundof music by selecting the weight and the spring constant. This alsomakes it possible to place an accent on a musical composition outputfrom the actuator. Thus, the actuator operates also as a woofer. It istherefore possible to produce outputs ranging from a bass sound to ahigh-pitched sound from one device for a small-sized audio system. It ispossible to provide an earphone or headphone that operates like atwo-way or a three-way speaker.

FIGS. 8 and 9 show another example of a vibration actuator used in anearphone or headphone of the present invention.

The structure of this vibration actuator comprises, like the vibrationactuator of FIG. 3, a magnetic circuit of an internal magnet structurein which a permanent magnet 102, a yoke 101, and a plate 103 are fixedtogether by a center shaft 107 such as a bolt or a pin, a suspension 104formed by a single piece of an arc-shaped helical leaf spring supportingthe magnetic circuit, a vibration transmitting portion 108 in the shapeof a hollow case fixing an outer end of the suspension and having astopper 110, a diaphragm 105 having an outer end fixed to the vibrationtransmitting portion, a coil 106 attached to a coil fixing portion 109of the diaphragm 105 and disposed in a magnetic gap of the magneticcircuit, and an upper cover 111 and a lower cover 112 closing upper andlower openings of a hollow portion of the vibration transmitting portion108. The lower cover 112 also serves as a stopper for preventing plasticdeformation of the suspension 104 caused by excessive vibration of themagnetic circuit.

The vibration actuator of FIG. 8 is different from that of FIG. 3 inthat the shape of an outer peripheral portion of the yoke 101 differsfrom that of the yoke 31 in FIG. 3, that the terminal table 44 is notprovided, and that sound release holes are also formed in the uppercover 111 and a sound release hole of the lower cover is a large hole.

Referring to FIG. 9, a terminal 114 is disposed on an inner surface ofthe lower cover 112. The terminal 114 is connected to an unillustratedlead wire of the coil 106. A signal for driving the coil is applied fromthe terminal 114. The terminal 114 may be a coil spring, a leaf spring,a connector, a gold-plated pad, or the like.

As a material of the lower cover 112, use may be made of any material,such as resin, rubber, cloth, paper, glass epoxy resin, other insulatingmaterials, or insulating composite materials as long as it serves as aninsulator.

As a material of the terminal 114, use may be made of any material, suchas copper, gold, silver, other conductive materials, or conductor-platedor -printed materials as long as it serves as a conductor.

According to this embodiment, it is not necessary to project theterminal table outward from the vibration transmitting portion.Therefore, the vibration actuator can be reduced in outer dimension and,as compared with the vibration actuator in FIG. 3, can be easilyincorporated into the earphone or headphone.

FIGS. 10 and 11 show another vibration actuator used in the presentinvention. The structure of this vibration actuator also comprises, likethe vibration actuator of FIG. 3, a magnetic circuit of an internalmagnet structure in which a permanent magnet 302, a yoke 301, and aplate 303 are fixed together by a center shaft 307 such as a rivet, abolt, or a pin, a suspension 304 formed by a single piece of anarc-shaped helical leaf spring supporting the magnetic circuit, avibration transmitting portion 308 in the shape of a hollow case fixingan outer end of the suspension, a diaphragm 305 having an outer endfixed to the vibration transmitting portion, a coil 306 attached to acoil fixing portion 309 of the diaphragm 305 and disposed in a magneticgap of the magnetic circuit, an upper cover 310 and a lower cover 311having sound release holes 316, which close upper and lower openings ofa hollow portion of the vibration transmitting portion 308, a terminaltable 312 projected outward from a portion of the vibration transmittingportion, and a terminal 313 attached to the terminal table.

The vibration actuator of FIG. 10 is different from the vibrationactuator of FIG. 3 in that the vibration transmitting portion 308 of theformer has a staircase-like stepped portion 314 formed at its inner wallportion and hat sound release holes 315 are formed at portions of thisstepped portion. The stepped portion 314 is formed into a stair-climbingshape climbing up from the lower cover 311 toward the upper coveroutward in the radial direction of the vibration transmitting portion.In the illustrated example, the suspension 304 is attached to the secondstair and prevents rolling of the magnetic circuit. The sound releaseholes 315 are formed at the third stair so as to penetrate therethroughdownward. The diaphragm 305 is fixed to the fourth stair.

Based on these differences from the vibration actuator of FIG. 3, thevibration actuator of FIGS. 10 and 11 can ensure a sound pressurecharacteristic thereof even when a printed board, a panel, or any otherwall member exists in contact with the back of the vibration actuatorand a sufficient back cavity cannot be ensured.

FIG. 14 shows a sound pressure characteristic of the vibration actuatorshown in FIGS. 11 and 12 (with the panel attached on its back). It isseen that the characteristic can be improved by 2 to 3 dB between 500 Hzand 8 kHz as compared with the prior art.

Therefore, the vibration actuator of FIG. 10 is suitable for use in anearphone or headphone having a structure where a casing wall iscontacted with the back of the vibration actuator.

In the foregoing embodiments of FIGS. 3, 8, and 10, the bolt, the rivet,the pin, or the like is used as the center shaft of the magneticcircuit. Instead, the yoke, the plate, and the permanent magnet may befixed by the method of bonding or the like.

Normally, as a device for making an acoustic transducing element be inclose vicinity to an ear, use is typically made of a headphone of thetype in which an acoustic transducing element is pressed against the earby wearing a cranial headband or a neckband. Besides, there are an innerear type in which the element is inserted into an auricle of ear andretained therein (often called an earphone in distinction from aheadphone), and an ear fit type in which a support arm is hooked overthe ear to dispose the element on the side of the ear.

In the present invention, the term of an “earphone or headphone” is usedfor collectively referring to the foregoing three types.

1. An earphone or headphone having a vibration actuator mounted as an electroacoustic transducer, said vibration actuator comprising: a magnetic circuit including a permanent magnet, a yoke, and a plate used for concentrating magnetic flux of said permanent magnet and which has a magnetic gap at a portion thereof; a coil disposed in the magnetic gap of said magnetic circuit; a vibrating plate attached with said coil and imparted with a driving force by said coil; a suspension formed by a flexible spring and supporting said magnetic circuit; and a vibration transmitting portion fixing said suspension.
 2. An earphone or headphone according to claim 1, wherein, by simultaneously inputting a low frequency signal for generating a body sensible vibration and a signal for generating a sound and having a frequency higher than that of said low frequency signal, said vibration actuator simultaneously generates said body sensible vibration and said sound.
 3. An earphone or headphone according to claim 1, wherein, in said vibration actuator, said magnetic circuit vibrates in response to an input signal of a low-band frequency that generates a body sensible vibration and a low-pitched tone, both of said vibrating plate and said magnetic circuit vibrate in response to an input signal of an intermediate-band frequency, and said vibrating plate vibrates in response to an input signal of a high-band frequency to produce a high-pitched tone.
 4. An earphone or headphone according to claim 1, further comprising a cover covering an outer side and a terminal for electrical connection, said terminal being disposed on said cover.
 5. An earphone or headphone according to claim 4, wherein the terminal for electrical connection is provided inside a vibrator.
 6. An earphone or headphone according to claim 4, wherein said cover has a sound release hole for air viscosity attenuation.
 7. An earphone or headphone according to claim 1, wherein the vibration actuator has a stepped structure disposed at an outer periphery of said magnetic circuit to protect rolling of said magnetic circuit.
 8. An earphone or headphone according to claim 7, wherein said stepped structure has an air hole.
 9. An earphone or headphone according to claim 1, wherein, in said vibration actuator, said magnetic circuit has a vibration resonance frequency between 60 Hz and 300 Hz.
 10. An earphone or headphone according to claim 9, wherein the earphone or headphone allows bodily sensation of “a vibration sound” felt by tactile sense.
 11. An earphone or headphone according to claim 9, wherein the earphone or headphone allows bodily sensation of “a tactile sound” felt by tactile sense.
 12. An earphone or headphone according to claim 9, wherein the earphone or headphone allows bodily sensation of “a conduction sound” felt by tactile sense.
 13. An earphone or headphone according to claim 2, wherein, in said vibration actuator, said magnetic circuit vibrates in response to an input signal of a low-band frequency that generates a body sensible vibration and a low-pitched tone, both of said vibrating plate and said magnetic circuit vibrate in response to an input signal of an intermediate-band frequency, and said vibrating plate vibrates in response to an input signal of a high-band frequency to produce a high-pitched tone. 